GNU bug report logs - #35557
26.1; false positive: Match data clobbered by buffer modification hooks

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Package: emacs; Reported by: David Bremner <david@HIDDEN>; Keywords: moreinfo; dated Sat, 4 May 2019 11:37:01 UTC; Maintainer for emacs is bug-gnu-emacs@HIDDEN.

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From: Stefan Kangas <stefan@HIDDEN>
To: Paul Eggert <eggert@HIDDEN>
Subject: Re: 26.1; false positive: Match data clobbered by buffer
 modification hooks
In-Reply-To: <64899525-fd17-c715-dff4-b99996717f4f@HIDDEN> (Paul Eggert's
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References: <64899525-fd17-c715-dff4-b99996717f4f@HIDDEN>
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Paul Eggert <eggert@HIDDEN> writes:

> I tried to reproduce the bug and failed, so I'm afraid you'll have to step in
> and help debug it. First, please use 26.2 rather than 26.1. Second, please 
> simplify the ./configure arguments (there are some duplicates, and
> --enable-libsystemd isn't the right name for the flag). Third, I suggest running 
> it under GDB and seeing what exactly goes wrong, e.g., by putting a watchpoint
> on search_regs.start[sub].

I couldn't reproduce this bug either.

David, could you please look into the above suggestions by Paul?

Best regards,
Stefan Kangas




Information forwarded to bug-gnu-emacs@HIDDEN:
bug#35557; Package emacs. Full text available.
Added tag(s) moreinfo. Request was from Stefan Kangas <stefan@HIDDEN> to control <at> debbugs.gnu.org. Full text available.

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To: David Bremner <david@HIDDEN>
From: Paul Eggert <eggert@HIDDEN>
Subject: 26.1; false positive: Match data clobbered by buffer modification
 hooks
Organization: UCLA Computer Science Department
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I tried to reproduce the bug and failed, so I'm afraid you'll have to step in 
and help debug it. First, please use 26.2 rather than 26.1. Second, please 
simplify the ./configure arguments (there are some duplicates, and 
--enable-libsystemd isn't the right name for the flag). Third, I suggest running 
it under GDB and seeing what exactly goes wrong, e.g., by putting a watchpoint 
on search_regs.start[sub].




Information forwarded to bug-gnu-emacs@HIDDEN:
bug#35557; Package emacs. Full text available.

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From: David Bremner <david@HIDDEN>
To: bug-gnu-emacs@HIDDEN
Subject: 26.1;
 false positive: Match data clobbered by buffer modification hooks
Date: Sat, 04 May 2019 08:35:57 -0300
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1. Save the following as test.el

(let ((inhibit-modification-hooks t))
  (with-temp-buffer
    (insert "P'")
    (goto-char (point-min))
    (while (re-search-forward "\\([^\\]\\)'" nil t)
      (replace-match    "\\1`"))
    (buffer-substring (point-min) (point-max))))

2. run "emacs --batch --quick --load ./test.el"

3. Under docker, with Debian's emacs-nox (but not emacs-lucid or
   emacs-gtk, I get an error "Match data clobbered by buffer modification
   hooks".

I don't think this is Debian specific, as someone was also able to
duplicate it with "nixpkgs.emacs26-nox" (also in Docker).
   
I agree the setup sounds pretty specific, but it is used by a Debian CI
setup, which is why I care.

Here's the build info, copied out of docker:

In GNU Emacs 26.1 (build 2, x86_64-pc-linux-gnu)
 of 2019-02-03, modified by Debian built on zam904
Recent messages:
Loading /etc/emacs/site-start.d/00debian.el (source)...done
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --enable-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/sh\
are/emacs/26.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --build
 x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
 --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/sh\
are/emacs/26.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --with-x=no
 --without-gsettings 'CFLAGS=-g -O2
 -fdebug-prefix-map=/build/emacs-26.1+1=. -fstack-protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'




Acknowledgement sent to David Bremner <david@HIDDEN>:
New bug report received and forwarded. Copy sent to bug-gnu-emacs@HIDDEN. Full text available.
Report forwarded to bug-gnu-emacs@HIDDEN:
bug#35557; Package emacs. Full text available.
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Click here to see this page with the latest information and nicer formatting.
Last modified: Mon, 25 Nov 2019 12:00:02 UTC

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